What happened to the smaller size promise?

When the mirrorless cameras were introduced we were promised that it would mean smaller cameras. Yet they have not really made good on that promise. Sure current cameras are smaller than the DSLRs but not by all that much.

The smallest you can currently get is the Pentax Q - but it use a tiny sensor. Looking at the Pentax made me think of another Pentax from more than 30 years ago - the Pentax Auto 110. As the name implies it used 110 film it and was very small (and cute).

The surprising thing is that even though it was the same size as the Pentax Q it had room for a mirrorbox and the film frame was the same same size as mFT. So why hasn't anyone gone really small with a decent size sensor? If is was done as a mirrorless system it could be even smaller than the original Pentax Auto 110!

Provided it wouldn't be too expensive would you like a camera like that?